Thread bobbin



THREAD BOBBIN Filed April 5, 1952 W. E. THOMPSON, JR.. ET AL April 6,1954 1m! E9221)? Fggmandl. arf

ATTOR s Patented Apr. 6, 1954 UNITED STATES- ATENT OFFICE THREAD BOBBINApplication April 3, 1952, Serial No. 280,434

8; Claims. 1

This invention relates to bobbins formed of continuous filament threadand has for its object the provision of improved bobbins and a method ofmaking them. The bobbins of our. invention are formed of continuousfilament thread formed of filament-formingsynthetic, resinshaving. anexterior coating of synthetic resinuous material and are compressedwhile the coating material is at adhesive consistency in the direc--nylon, Orlon (polyacrylonitriles), Saran (copolymers of vinylidene andacrylonitrile), Dacron (polyethylene glycol terephthalate), and

Vinyon N (copolymer of vinyl chlorideandac rylom'trile) are relativelydenseand smooth and have the property of plastic memory in varyingdegrees. end-fibers, such as characterize the thread formed. of staplesynthetic filaments and naturalfibers, the bobbins formed of continuousfilament thread unravel freely and this results in delays in their use.Ifbobbins'formedof these continuous filament threads were compressed,axially, they would springback on release ofithe pressure because of thesmoothness, resiliency, andplastic memory of the thread.

It'has been the practice heretofore in making bobbins of such continuousfilament threads'to wind the thread on paper acres whichsupport thebobbins internally and thento-attach paper sides to the paper core tosupport the bobbins on.

the sides. Even withthis expediency, they. are relatively loose andcontain muchlesslengthof thread than they would have in a compressed.state. The unravelling annoyance is still present and a cause of. muchdelay and loss of thread. Moreover, the bobbin shells occupy space thatis utilized with thread in the bobbins" of the inven-- tion.

Bobbins having paper shells or metalbobbins for useain sewing machines:have a tendency to:

Because of the, absence-of projecting spin and release thread whichcauses an entanglement, thus forcing an interruption of stitching. Thisis particularly noticeable upon stopping and starting of the machine innormal operation.v Bobbins produced by our method decrease in. diameteras the thread is used resulting in. a constant peripheral speed, whereasthe conventional bobbins has a progressively increasing peripheralspeed. Therefore, the tend-- ency to spin is greatly reduced in the useof bobbins manufactured in accordance with our invention Inaccordancewith the method of our invention, we apply to th exterior surfaces of acore strand of continuous filament synthetic threads a thin coating ofathermoplasticsynthetic resinone material that softens to adhesiveconsistency atv temperatures above F., and wind the thread, preferablyby standard cross-wind'means to form bobbins of relatively low densityand considerably larger in axia1 thickness than. required for use in theintended machine. The synthetic resinousmaterial of the coating is notadhesive at normal temperatures: and is more compressible than the corestrand. The bobbins are preferably placed over anarbor orpin to retaintheir internal dimensions and are com-- pressed inthe direction of theiraxes of rotation while at a temperature at which the resin ous coatingissoftened toeifect adhesive bonding under pressure. The bobbins arereduced in. thickness at least 20%, and most advantageously to around30%, thereby excluding most of; the air, and forcing theadjacentconvolutions of thread into a positivebut weak side-to-side adhesivebonding. On coolin and release of pressure, the bobbins sprin back but asmall amount and do not unravel with normal handling. It is advantageousto form bobbins having uniformly fiat sides and this is accomplishedaccording to the invention by pressing the bobbins between dies havingsloped, e. g., conically shaped surfaces, to compress the bobbinsmore-near theircenters than near their peripheries because there is agreater tendency, to spring,

back at the center which diminishes progressively in the direction. oftheir perimeters.

One important characteristic of the bobbins of:

The accompanying drawing illustrates more Or less diagrammatically, insectional elevation, an arrangement of apparatus suitable for formingproved bobbins of the invention especially intended for use in sewingmachines.

The apparatus illustrated in the drawings comprises a frame I in which aplurality of upp die blocks 2 is mounted, a movable central frame 3 onwhich a plurality of lower die blocks i is mounted, and a movable lowerframe on which a plurality of cylindrical pins or arbors 6 is mounted.The frame I is preferably fixed, while the frames 3 and 4 arereciprocable in an upward and downward direction. The frames I, 3 and 5are preferably heated to a sufliciently elevated temperature that thedie blocks 2 and 4 and the arbors 6 are heated by conductivity to therequisite temperature for heating the bobbins.

In a preferred embodiment of the invention, the compression faces of thedie blocks 2 and 4 are conically shaped, the angles a varyin from 1 to 5to the end that the centers of the bobbins are compressed more than theedges.

The method of the invention will now be described with particularreference to nylon continuous filament thread, it being understood thatthe method may be applied with slight variations that will be apparentto those skilled in the art to the other continuous filament threadsherein mentioned.

Nylon thread, twisted or braided, in varying sizes such as may be usedin winding bobbins for sewing machines, net-tying machines, andlacemaking machines, is coated with a synthetic resinous material in anysuitable manner. The coating is preferably one that becomesthermoplastic to adhesive consistency at temperatures above 140 F. andwhich is not tacky at ordinary temperatures. United States LettersPatent 2,590,586 of Walter E. Thompson, Jr. and Rollin W. Taylordescribes resinous coating materials and methods of application whichmay be utilized in carrying out a method of the invention. We .prefer touse the thermoplastic coating materials described in the patent.

We shall now describe the invention in the formation of our improvedbobbins from a nylon thread made of 210 denier nylon, spun 13 turnsright, matched three cord, and twisted 11 turns left.

A first coating is prepared by dissolving part of 66 nylon flake in asolution. consisting of 2 parts of water and 8 parts of ethyl alcohol(all parts by Weight).

A second coating is prepared by forming a solution comprising 110 partsof ethyl alcohol, 2 parts polyvinyl butyral, and A part oleic acid (allparts by weight).

In applying the coatings, the nylon thread is first run through a bathof the first coating, then through a drying chamber as described inconnection with Fig. 1 of the said patent. The sec-- ond coating isapplied over an emulsion roll at the time of winding the bobbin. Thepurpose of the second coating is to diminish the strength of the firstcoating and eliminate jerking in unwinding; For sewing machine bobbinswe may eliminate the first coating and just use the second coating byusing a higher concentration of resin than in the above coating. Whilethe patent describes the application of coatings containing from 10% toof resin on the basis of the weight of the core, such amounts ofcoatings are usually applied only when making bobbins for fishnets, andthe like. It is to be understood that for thread to be made into sewingmachine bobbins we prefer to use considerably thinner coatings.

The coated thread when at a temperature below the softening point of thecoating is wound into cross-wound bobbins in any suitable manner. Weprefer to wind the bobbins under an appreciable tension. When using acoating of the type just described, the bobbins are preferably placed ina chamber where they are allowed to become conditioned at a relativehumidity of 40-44% at a temperature of about F. The absorbed moistureaids in suppressing the plastic memory when the bobbins are heated underpressure and results in better dimensional stability. The term plasticmemory is used herein to define that tendency of certain syntheticresinous materials to return to their original state after having beenelongated. In the case of nylon thread and other thread having similarplastic memory characteristics, the suppression of plastic memory in theheating during-coating can be undone if the heating during bobbincompression is at temperatures around 250 F. in the absence of moisture.We, accordingly, prefer to heat the bobbins during compression when in asuitably moist condition.

The bobbins may be left under these moisture conditions for around 24hours. The conditioned bobbins B are placed over the arbors 6 which areelevated to project above the die blocks 4 and then frames 3 and 5 areraised, the arbor 6 entering the central opening of die block 2. Asuincient pressure is applied to reduce the thickness of the bobbins atleast 20% as measured in the direction of the axis of the arbor which isthe axis of rotation of the bobbin. We prefer, however, in forming nylonbobbins to reduce the thickness to from 30% to 35%. The die blocks andarbors are at such temperatures that the nylon bobbins are heated totemperatures of about 260 F. and the pressure is maintained for about 60seconds. After the compression and heating have been completed, theframe 5 is lowered to pull the arbor out of the top die block and thenframe 3 is lowered slightly, at which position it is held for around 10seconds to allow the bobbins to set. Following this, frames 3 and 5 arelowered to remove the bobbins.

In one preferred operation, we use die blocks in which the angle a isabout 2. These die blocks give the bobbin a concave surface when underpressure, as shown by the broken lines, but when the pressure isreleased, the bobbins expand much more at the centers than at theirperipheral edges and assume the dead flat shape shown in full lines.

A typical bobbin formed of nylon thread in the operation above describedhad an initial thickness in its axial direction of 0.640 in. and aftercompression and relaxation a thickness measured in the same direction of0.420 in. which is a reduction in thickness of 35%. Other bobbinssimilarly formed having an initial thickness of 0.525 in. beforecompression and 0.360 in. after compression were reduced in thickness32%.

In forming bobbins of Dacron thread, we prefer to follow the samepractice described in connection with the use of nylon. In formingbobbins of Orion, however, we prefer to heat the bobbins to atemperature of around F. and to hold the bobbins while under compressionfor about 45 seconds.

Bobbins formed of the continuous filament thread herein described areusually wound over ae'zgew &1 the-core of a bobbin shell: which hasretaining sides later pressed on to. prevent, unravelling. Even when soprotected; the loose thread unwindsfreely and can easily becomeentangled'i.

Thecore and supporting side; members occupy considerable space, asinthe-shuttle of asewing machine. 'Iheimprovedbobbin of the invention isvery dense and can. be shaped to occupy the maximum space in the machinewhere it is intended to be used. It can be handledwithout unravelling.As anindication of their unraveliling properties, the bobbins of theinvention (with the end of thread unsecured) can be thrown against awall as one would throw a baseball without causing unravelling.Notwithstanding this property, the bobbin can be unwound smoothly andwithout the necessity for undue tension, as by the tension of a sewingmachine feed. Another important characteristic of the bobbins of theinvention is their dimensional stability. The importance of dimensionalstability is emphasized by the fact that the bobbins can be producedwith such close uniformity that they do not vary more than 0.005 in. inthickness. The bobbins do not appreciably change shape. For example,nylon bobbins of the invention may be exposed to atmospheric conditionsof high humidity at normal temperatures without changing shape to anyappreciable extent. We attribute the characteristics of our improvedbobbins to the combination of the coating and the compression. Thecompression removes substantially all of the air from the bobbin andbrings the adjacent convolutions of thread into side-to-side bondingcontact. The threads while in the bobbin appear to have some ellipticitywhereby there is appreciable side-to-side attachment.

The bobbins of our invention may be of the type that are unwound fromthe inside or from the outside. Bobbins for use in standard sewing areusually unwound from the outside. Bobbins of the type used for makingfishnets can b unwound from the inside or from the outside dependingupon the kind of machine used.

In producing bobbins of nylon thread, for example, the thread may becoated with such an amount of resin coating material as to consist offrom to 20% of the weight of the coated thread. Such amounts of coatingare suitable for forming bobbins for use in making fishnets which areknot retentive, as described in said patent. When the bobbins are to beused in standard sewing machines, satisfactory bobbins can be formedfrom thread having coatings consisting of from 1% to 10% of the weightof the coated thread.

The aforementioned patent is concerned primarily with water-insolublecoating resins. This invention is not limited to the use of waterinsoluble coating materials and utilizes water-soluble coating materialsuch as polyvinyl alcohol for thread to be used in sewing machines andlace-making machines.

In the foregoing description, we have emphasized the production ofbobbins having fiat sides because such bobbins give improved results inunwinding and contain the maximum amount of thread on the basis ofdiameter. However, we may use dies that will give the faces a curved orrounded surface.

We claim:

1. A bobbin of the kind described consisting of a continuous-filamentthread comprised of a core of synthetic resinous material of a typewhich normally has substantially plastic mem- Dry and an exteriorcoating of a thermoplastic resinous material which is more compressibleof 'the bobbin, adhering'to one another with sufficient tenacity toprevent unraveling in normal handling but with insuificient tenacity toprevent unwinding when subjected to unwinding tension, thetightly-compacted condition of the thread and the adherence of theconvolutions thereof to one another being the result of axialcompression of the bobbin While heated to a temperature above thesoftening point of the resinous material of the threads, the plasticmemory of the resinous material from which the thread is formed havingbeen substantially suppressed, whereby the thread of the bobbin hasrelatively little plastic memory and the bobbin is dimensionally stable,the bobbin having a relatively great length of thread on the basis ofits cubic content.

2. A bobbin as defined in claim 1 in which the core of the thread isformed of a synthetic resin from the group consisting of nylon,polyethylene glycol terephthalate, polyacrylonitrile, and copolymers ofvinylidene chloride and acrylonitrile.

3. The method of producing a bobbin of continuous filament thread whichcomprises winding a bobbin of a thread of synthetic resinous materialhaving a surface which softens at temperatures above F., compressing thebobbin in the direction of its axis sufficiently to affect a substantialreduction in thickness of the bobbin axially thereof and sufficiently tforce the adjacent convolutions of the thread into tightly compactedrelationship axially of the bobbin, subjecting the bobbin, during thecompressing operation, to a temperature at least as high as thesoftening point of the resinous material from which the thread is made,and maintaining the bobbin under pressure while subject to such lattertemperature for a length of time sufficient to bring about softening ofthe surface of the thread and the securing of the convolutions thereofinto adhesive contact axially of the bobbin, whereby the bobbin will notunravel under normal handling but will unravel freely under an unwindingtension.

4. The method of producing a bobbin as defined in claim 3 in which thethread is of a synthetic resinous material normally having substantialplastic memory and in which the bobbin is compressed while in a moistcondition an is maintained at a sufficiently high temperature whilemoist for a length of time sufiicient to substantially suppress theplastic memory of the resinous material thereof.

5. The method of producing a bobbin as defined in claim 3 in which theresinou material from which the thread is formed is a synthetic resinselected from the group consisting of nylon, polypolyethylene glycolterephthalate, polyacrylonitrile, and copolymers of vinylidene chlorideand acrylonitrile.

6. The method of producing a bobbin as defined in claim 3 in which thebobbin is compressed to efiect a reduction of at least 20% in thickness.

'7. The'method of producing a, bobbin as de- References Cited in thefile of this patent fined in claim 3 in which the bobbin is compressedbetween convexly-shaped dies having a UNITED STATES PATENTS slope offrom 1 to 5 to compress the bobbin Numb r Name Date more in the centerthan at the periphery. 5 675,801 Stiles June 4, 1901 8. The method ofproducing a bobbin as de- 1,135,470 Tolman Apr. 13, 1915 fined in claim3 in which the bobbin. after it has 2,001,977 Riddell May 21, 1935 beenreduced in thickness to the desired degree, 2,025,920 Webber Dec. 31,1935 is held under pressure for a. short period to set 2,448,114 Olsonet a1. Aug. 31, 1948 the resinous material, th pressure to which the 102,488,890 Anderson Nov. 22, 1949 bobbin is subjected i relieved and thebobbin is 2,564,941 Wellman Aug. 21, 1951 permitted to remain beforeremoval for a short while t relax.

